Sipes are commonly provided in a tread surface in order to enhance water absorption in order to enhance traveling performance on wet road surfaces and icy and snowy road surfaces. However, if an excessive number of sipes are disposed in the tread surface, the tread rigidity will decline, leading to steering stability and braking ability being negatively affected. Therefore, conventionally, various technologies have been proposed regarding the form and arrangement of the sipe (e.g. see Japanese Unexamined Patent Application No. H9-263111A and Japanese Unexamined Patent Application Publication No. 2006-27306A).
Of these, Japanese Unexamined Patent Application No. H9-263111A describes enhancing steering stability on ice while preventing damage such as the sipes cracking or chunks being taken out of the tire by disposing two or more sipes in a block face that extend in mutually differing directions so as to cross. Additionally, Japanese Unexamined Patent Application Publication No. 2006-27306A describes enhancing riding comfort while ensuring steering stability and wet braking performance by providing a sipe with a shape having a twist around a twisting axis that extends in a tire radial direction.
However, in the case of Japanese Unexamined Patent Application No. H9-263111A, while the water absorption of the tread surface is enhanced to a certain degree, there is a limitation in that it becomes difficult to maintain steering stability if further enhancements of the water absorption are attempted. Additionally, in the case of Japanese Unexamined Patent Application Publication No. 2006-27306A, due to the twist angle being set to a size reaching 135° and greater, there are problems such as releasability from a mold after the tire is vulcanization molded being negatively affected and the tread surface becoming easily damageable.